Thank you for providing the request ID. Having a look in our logs, the error I am seeing is a 422 unprocessable entity. Usually this means that one or more of the fields in the request is incorrect, or the json itself is malformed. You can see an example fulfillment call in our documentation here: https://shopify.dev/api/admin/rest/reference/shipping-and-fulfillment/fulfillment#create-2021-07
Thank you for your response.
I created a fresh order and went through the flow.
1. I did an api request for the order.
2. I accepted the order
3. I tried to create a fulfillment
I used the following body which is taken from the documentation with only the location_id being changed